The field experiments were carried out in two successive summer seasons of 2014 and 2015 at the experimental farm
of the Faculty of Agriculture, Menoufia University, in El-Raheb, Egypt to evaluate yellow inbreed lines of maize through
line x tester analysis.
Top crosses were made each of the twenty-five S4 lines and the two testers by hand to give a total of 50 top crosses in
2014season. In the second season (2015) two adjacent experiments were conducted under two plant densities. The first
experimental represented a normal plant density (ND) of 24000 plant/fad., (hills spaced 25 cm apart and one plant/ hill).
The second experimental represented plant density (HD) of 30000 plants/fad. (hills spaced 20 cm a part and one plant
hill). In each experiment the 50 top crosses as well as the two checks hybrids Giza 168 and Giza 176 were grown in a
Randomized Complete Block Design with three replications. Performance of inbred lines varied with plant densities.
Parental lines L3, L4, L5, L14 and L23 were the best in mean performance and general combining ability effects under
this study. Results indicated that σ² SCA was more important than σ² GCA for all studied traits, plant height at the
combined analysis. Non-additive gene action was more affected by the interaction with environments than the additive
effects. The top crosses L12 x T2 and L17 x T2 showed desirable significant SCA effects for shortness and the low ear
placement under low plant density. Thirteen top crosses showed significant positive SCA effects for grain yield (ard/fad)
under HD, LD and combined analysis. Also, the top crosses L1 x T2 and L11 x T2 were significant under high plant
density. The top crosses (L3 x T1 and L14 x T2) and (L3 x T2) showed significant number of ears per plot and 100-kernel
weight relative to two check varieties for the top cross L3 x T1 gave the higher value of heterosis relative to the two
checks for ear weight and grain yield.